This invention generally relates to a method for the process for making hydrogen and carbon monoxide by partial oxidation reforming of a lower alcohol, e.g., methanol, and more particularly to a process for making acetic acid from a methanol feedstock and carbon monoxide obtained by partial oxidation of methanol.
In recent years, methanol production has increased in countries with high gas production due the development of high capacity plants utilizing high yield processes, for example, the Mega-methanol technology. Market conditions in different locations can often result in relatively low methanol prices (in the case of an oversupply) and relatively high natural gas prices (in the case of a shortage), due generally to excessive usage in the heating of buildings and homes, and as well as high usage in power plants. For example, in chemical plants where syngas is produced for the purpose of extracting CO for the synthesis of acetic acid, high costs can make natural gas cost prohibitive as a feedstock.
The primary raw materials in acetic acid manufacture are carbon monoxide (CO) and methanol. By retrofitting existing methanol plants to include acetic acid synthesis units, it is possible to eliminate the step of importing methanol for the synthesis of acetic acid, instead producing methanol in situ for the acetic acid synthesis. The retrofit of existing methanol plants for the manufacture of acetic acid is known in the art. Representative references disclosing this and similar processes include U.S. Pat. No. 6,232,352 to Vidalin, U.S. Pat. No. 6,274,096 to Thiebaut et al, and U.S. Pat. No. 6,353,133 to Thiebaut et al, each of which is hereby incorporated by reference.
In U.S. Pat. No. 3,920,717, Marion discloses a continuous process for the production of methanol from solid and/or liquid hydrocarbon material in a catalyst free reaction zone using a partial oxidation reactor. In U.S. Pat. No. 4,006,099, Marion et al. disclose improved combustion efficiency in the non-catalytic partial oxidation of liquid hydrocarbonaceous materials in a double-annulus-type burner. In U.S. Pat. Nos. 4,081,253 and 4,110,359, Marion discloses a method for producing synthesis gas, substantially comprising H2 and CO and having a mole ratio (H2/CO) of about 0.5 to 1.9 by partial oxidation of a hydrocarbonaceous fuel with substantially pure oxygen.
The use of partial oxidation reactors for the reforming of natural gas feedstock to syngas is well known in the art. Representative references disclosing partial oxidation reactors for the production of syngas include U.S. Pat. No. 2,896,927 to Nagle et al; U.S. Pat. No. 3,920,717 to Marion; U.S. Pat. No. 3,929,429 to Crouch; and U.S. Pat. No. 4,081,253 to Marion, each of which is hereby incorporated herein by reference.
The manufacture of hydrogen from methanol using a methanol reforming catalyst alone or in conjunction with a hydrogen-generating shift reactor is known in the art. Representative references disclosing this and similar processes include U.S. Pat. No. 4,175,115 to Ball et al; U.S. Pat. No. 4,316,880 to Jockel et al; U.S. Pat. No. 4,780,300 to Yokoyama; and U.S. Pat. No. 6,171,574 to Juda, each of which is hereby incorporated herein by reference.
The manufacture of acetic acid from carbon monoxide and methanol using a carbonylation catalyst is well known in the art, as demonstrated by representative references disclosing this and other similar processes including U.S. Pat. No. 1,961,736 to Carlin et al; U.S. Pat. No. 3,769,329 to Paulik et al; U.S. Pat. No. 5,155,261 to Marston et al; U.S. Pat. No. 5,672,743 to Garland et al; U.S. Pat. No. 5,728,871 to Joensen et al; U.S. Pat. No. 5,817,869 to Hinnenkamp et al; U.S. Pat. Nos. 5,877,347 and 5,877,348 to Ditzel et al; U.S. Pat. No. 5,883,289 to Denis et al; and U.S. Pat. No. 5,883,295 to Sunley et al, each of which is hereby incorporated by reference herein.
The primary raw materials for vinyl acetate monomer (VAM) manufacture are ethylene, acetic acid and oxygen. Carbon dioxide is produced as an undesirable byproduct in the reaction and must be removed from the recycled ethylene. A significant expense of new production capacity for syngas, methanol, acetic acid and acetic acid derivatives such as VAM, is the capital cost of the necessary equipment. Other significant expenses include the operating costs, including the cost of raw materials. It would be desirable if these capital and operating costs could be reduced.
As far as applicant is aware, there is no disclosure in the prior art for supplying a methanol feedstock to a partial oxidation reactor to produce hydrogen and carbon monoxide for the synthesis of acetic acid. Further, as far as applicant is aware, there is no disclosure in the prior art for modifying existing methanol plants having partial oxidation reactors to reform a lower alcohol, e.g. methanol, in the presence of carbon dioxide, oxygen, steam or a combination thereof.